Oysters Are Munching On Our Microplastics

Tiny pieces of plastic may endanger Pacific oysters by adversely affecting their reproduction, according to a new study. They may have similar effects on other marine bivalves, raising questions about their impacts on marine ecosystems more broadly.

The plastic pieces are known as microplastics are, which are defined as being anywhere from 5 mm in size to just 1 nanometer (0.000001 mm). Scientists refer to primary microplastics and secondary microplastics: the former are intentionally manufactured super-small, primarily used in cosmetics and personal care products, industrial scrubbers used for abrasive blast cleaning, microfibers used in textiles, and pellets used in plastic manufacturing processes; the latter are the result of larger pieces of plastic disintegrating over time.

Imagery of plastic pollution in the ocean often focuses on more visible impacts, such as trash that has become entangled around the neck of a marine mammal, or the appalling sight of vast amounts of plastic in the stomachs of seabirds on Midway Atoll. It is of course far harder to demonstrate the impacts of pollution that can not be seen, but those impacts are very real.

One of the great problems with microplastics is their ubiquity: It has been estimated that the ocean contains 5 trillion particles, totaling 250,000 tons, while a study last yearconcluded that 100,000 microbeads entered the ocean with each use of a personal cosmetic product that contained them. (The United States recently banned the production of personal care products containing microbeads from July 2017.) Just one cubic meter of ocean water may contain as many as 100,000 particles.

This is a problem particularly for filter feeding organisms such as mussels, sea cucumbers and some zooplankton, which may unintentionally consume large amounts of microplastics, which are often approximately the same size as their phytoplankton prey. Studies have shown that this can have adverse effects on those species' energetics - unsurprisingly, as eating food-sized plastic is no substitute for eating actual food - as well as, in some cases, having immunological and neurological impacts. An additional concern is the leaching of chemical additives and pollutants from the microplastics.

The latest study, published today in the Proceedings of the National Academy of Sciences, examined the effects of microplastic exposure on reproductively active Pacific oysters - a species the study's authors chose "because of its worldwide production, economic importance as seafood, and important role in estuarine and coastal habitats."

The authors established a number of tanks of oysters, which they fed phytoplankton, and in half of the tanks also introduced microplastics. Oysters that were exposed to microplastics readily ingested particles that were similar in size to the phytoplankton and, after two months of exposure, produced fewer and smaller oocytes (cells from which ova grow) and slower sperm, compared with those that weren't.

Furthermore, exposed oysters produced 41 percent fewer larvae, and those larvae grew at a slower rate and ultimately reached a size 18 percent smaller than larvae from the unexposed tanks.

The authors note that, "assuming no waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the marine environment from land is predicted to increase by an order-of-magnitude by 2025, especially in estuaries and coastal waters where oysters live and where waters are greatly influenced by increased human expansion."

Accordingly, they say, their study is something of an "early warning system" to help "limit the impact of the microplastic legacy in the decades to come."

Whole Foods, the Texas-based natural foods supermarket, no longer carries fish considered to be unsustainable.
The Whole Foods ban includes fish that is either overfished or caught in a harmful way, according to their website.
The popular Atlantic Halibut made the list, though the company will still sell Atlantic cod that is caught by hook and line or gillnets.
"Stewardship of the ocean is so important to our customers and to us," David Pilat, the global seafood buyer for Whole Foods told the New York Times. "We're not necessarily here to tell fishermen how to fish, but on a species like Atlantic cod, we are out there actively saying, 'For Whole Foods Market to buy your cod, the rating has to be favorable.'"
Here's a look at the list of fish that the superstore no longer sells and why.

Octopus
Whole Foods uses ratings set by the Blue Ocean Institute, a conservation group, and the Monterey Bay Aquarium in California.
The ratings are based on factors including how abundant a species is, how quickly it reproduces and whether the catch method damages its habitat.

Imported Wild Shrimp
"At Whole Foods Market, we've been saying that our mission is to sell only wild-caught fish that has been responsibly caught. For a few years now, we've used color-coded sustainability ratings, from green (best choice) to red (avoid), to help you make an informed choice. Now we're putting our mackerel where our mouth is: To support greater abundance in our oceans, we're no longer carrying red-rated wild-caught seafood!" the company wrote on its blog.

Tuna (from specific areas and catch methods rated "red")
On their website, Whole Foods says that they stopped selling "species that were extremely depleted in the oceans, such as orange roughy, shark and bluefin tuna" years ago.
The company uses the sustainability ratings of the Marine Stewardship Council (MSC).

Rockfish
According to the Monterey Bay Aquarium, "In recent years, reduced fishing has allowed many rockfish populations to recover from low levels. Gear concerns remain, however -- trawl-caught rockfish should still be avoided."

Sturgeon
According to Monterey Bay Aquarium, "Sturgeon farmed in the U.S. is a good alternative to most wild sturgeon, whose populations have seriously declined due to overfishing for sturgeon eggs (caviar)."

Trawl-Caught Atlantic Cod
Fishermen often catch cod with bottom trawl, large nets that skim across the seafloor.
Trawling, according to the Monterey Bay Aquarium, "damages marine habitats and produces bycatch."

Turbot
A cousin of Pacific halibut, turbot are a right-eyed flatfish -- as they develop, their left eye migrates across the top of the skull toward the other eye on the right side. Turbot are yellowish or grayish-brown on top and paler on their underside.